619 is the 12^{th} strobogrammatic number because it looks like the same number when it is turned upside down. The first 4 strobogrammatic prime numbers are 11, 101, 181, and **619**.

Print the puzzles or type the solution on this excel file: 10 Factors 2015-09-14

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- 619 is a prime number.
- Prime factorization: 619 is prime.
- The exponent of prime number 619 is 1. Adding 1 to that exponent we get (1 + 1) = 2. Therefore 619 has exactly 2 factors.
- Factors of 619: 1, 619
- Factor pairs: 619 = 1 x 619
- 619 has no square factors that allow its square root to be simplified. √619 ≈ 24.87971.

**How do we know that ****619**** is a prime number?** If 619 were not a prime number, then it would be divisible by at least one prime number less than or equal to √619 ≈ 24.9. Since 619 cannot be divided evenly by 2, 3, 5, 7, 11, 13, 17, 19, or 23, we know that 619 is a prime number.

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